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-   -   Remote Jump Start + Terminal Hot to touch - SOLVED (https://xoutpost.com/bmw-sav-forums/x5-e53-forum/110326-remote-jump-start-terminal-hot-touch-solved.html)

sevet 05-21-2019 07:29 PM

Remote Jump Start + Terminal Hot to touch - SOLVED
 
I helped a friend jump start their car yesterday and when I reached to open the cover to the jump start terminal located on the firewall, I noticed that it was incredibly hot.
As my X5 idled I noticed that the entire cable was hot. I checked for melted plastic but everything appeared intact.

The wire/cable is hot only when the engine is running.

As anyone encountered this before. I couldn't find anything for overheating jumper terminals. There was a thread for the cable covers melting at the positive battery terminal.
Thanks.

X5M-ISH 05-21-2019 08:19 PM

From an analytical point of view, a copper wire will become hot based off of several factors:
*the gauge of the copper wire is insufficient for the amount of amps traveling through it
*the length of the copper wire is insufficient for the amount of amps traveling through it
*poorly mated terminal and/or corrosion at the terminal
*poor battery ground or chassis ground or oxidization at the contact point(s)
*heat soak by virtue of the engine running and the close proximity of this positive lead in the engine bay

It doesn’t matter the case, but electrons hate traveling when hot. Heat in and of its self can increase resistance in copper wire...which makes more heat...which increases resistance. If the flow of electrons is great enough, the copper will generate enough heat to melt the protective covering of the wire or wherever the electrons have found for their path of least resistance (like a connector or terminal). I would suggest checking your battery terminals for a solid connection, check your grounds for a solid connection and no oxidization as well as check the integrity of the positive jumper lead for any damage to the plastic sheathing.

Of course if this is a commonly known thing for the e53, someone will jump in and comment soon enough.

sevet 05-21-2019 08:38 PM

Thanks.
I just took a good look at the terminal and noticed some corrosion on the nut holding the cable going to the starter.
Ordered a new terminal/box/cover and nuts.
Will swap it out.

andrewwynn 05-22-2019 03:08 AM

A high resistance connecting with lots of amperage can develop 1000s of watts. It will melt steel.

Copper is an extremely good conductor of HEAT as well as electricity so that is exactly why "the whole wire" was hot.

bcredliner 05-22-2019 02:43 PM

Might check to see if the cable gets hot with just the key on if you haven't already.

andrewwynn 05-22-2019 08:30 PM

There is no normal current path on the jumper terminal. I am willing to bet just not a great connection during the jump start generated a lot of heat at the connector.


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oldskewel 05-22-2019 11:10 PM

Quote:

Originally Posted by andrewwynn (Post 1162744)
There is no normal current path on the jumper terminal. I am willing to bet just not a great connection during the jump start generated a lot of heat at the connector.

On the 3.0i, doesn't that cable (that connects to the source cable at the jump port) go straight to the starter, and then another similarly sized cable continues on to the B+ terminal on the alternator?

So in addition to the obvious jump starting,

when starting the car, 200+ Amps flow through that junction (where the two cables connect, immediately behind the jump port nut) from the battery to the starter

and when the alternator is recharging the battery, the generated current flows from the alternator to the starter, through that junction, and on to the battery.


I would have first tried to file / sand off any corrosion. Completely agree about any surface resistance at that point being in a great spot to convert electrical energy into heat.

wpoll 05-22-2019 11:49 PM

Quote:

Originally Posted by oldskewel (Post 1162763)
On the 3.0i, doesn't that cable (that connects to the source cable at the jump port) go straight to the starter, and then another similarly sized cable continues on to the B+ terminal on the alternator?

So in addition to the obvious jump starting,

when starting the car, 200+ Amps flow through that junction (where the two cables connect, immediately behind the jump port nut) from the battery to the starter

and when the alternator is recharging the battery, the generated current flows from the alternator to the starter, through that junction, and on to the battery.


I would have first tried to file / sand off any corrosion. Completely agree about any surface resistance at that point being in a great spot to convert electrical energy into heat.

Not according to the wiring diagrams. The jumper B+ terminal (X6430) has zero current through it except when jump starting.

https://www.newtis.info/tisv2/a/en/e...rnator/sSnU3t5

The diagrams do have some variation though, including no mention of the X6430 terminal at all on some of the early version, so it's possible in some early cars that the connection arrangement is different.

andrewwynn 05-22-2019 11:55 PM

The B+ jump point is T connected to the main cable that goes from bat to Alternator to starter. Zero current unless jumping


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oldskewel 05-23-2019 12:36 AM

2 Attachment(s)
Quote:

Originally Posted by wpoll (Post 1162764)
Not according to the wiring diagrams. The jumper B+ terminal (X6430) has zero current through it except when jump starting.

https://www.newtis.info/tisv2/a/en/e...rnator/sSnU3t5

The diagrams do have some variation though, including no mention of the X6430 terminal at all on some of the early version, so it's possible in some early cars that the connection arrangement is different.

I agree, I can't guarantee how cars other than mine might be wired, and there should be plenty of reasonable options for the designers to pick from.

On my 06/2001 build 2001 3.0i, the cable on the back side of the jump port comes apparently directly from the battery.

Then at the jump port, it connects to a cable that runs to the starter, and the jump port nut screws on there. That cable you see coming out of the starboard side of the jump port cover goes directly to the starter solenoid.

Then there is a similar looking wire that runs from the starter to the B+ on the alternator.

I'll try to attach a couple of pics showing the connection at the starter. Pics taken when I had it all apart for the engine work last summer. The cable coming from above is the one that comes out of the jump port cover. The cable going to the left (in the photo) goes to the alternator.

Looking at that wiring diagram, it does show a photo indicating that X6430 is the jump port. But if that is wrong, and in fact X6404 is actually the jump port, then I will sign off on that wiring diagram. ;-)

I did a quick google and saw that the 4.4i is different from this - the jump port is at a terminal, and the battery goes to the alternator and then on to the starter at the end of the line. And the 3.0d is just like that too.

Attachment 76153

Attachment 76154

StephenVA 05-23-2019 09:56 AM

1 Attachment(s)
Multiple posters have discovered that the POSITIVE jump point is loose causing all types of issues. I would recommend, as everyone else has, remove the positive nut, cleaning all contact surfaces and reinstalling. I would also recommend removing the battery, cleaning all terminal ends and ground contacts in the trunk as any POOR negative grounds will create all kinds of electrical hell within the vehicle up to and including part failures and low voltage relays, and modules failures.

The parts under the hood have been exposed to high heat soaks, water spray, and general corrosion for the past 15 years. Give everything a wrench turn after cleaning.

Voltage drop Test listed below

oldskewel 05-23-2019 09:13 PM

And to experimentally verify that the jump port is in the circuit, I just did a quick test using my clamp ammeter on my 3.0i.

I clamped around the cable immediately to the starboard of the jump port cover.

When starting the engine, indicated current through that cable increased positively and then quickly (within about half a second) overloaded since it exceeded the 100-Amp range of my meter.

Then, following the start, while the engine was idling, current showed negative (driven by the 120A Valeo alternator, flowing back toward the battery) of 80 Amps, dropping to 60 after a few seconds, continuing to drop, which was enough to remove any doubt I may have had.

Like I said a couple of posts earlier, wiring diagrams on the internet show the 4.4i and the 3.0d having different setups (same as eachother, different vs. the 3.0i), where the jump port is at the end of the line. So in those cases, current won't flow past it except when jump starting or charging at the port.

But in the 3.0i, it's definitely in the normal path of high current. It makes perfect sense that any looseness or surface corrosion at the jump port would cause the port to get hot, and of course that should be fixed for many reasons.

Regarding the wiring diagram posted earlier, I think that branch coming off the alternator is just not there on my car. And I think the jump port is correctly indicated but mis-numbered as I suggested in that post.

sevet 05-26-2019 07:57 PM

Problem resolved.
 
Terminal replaced with one from a wreck.
Thanks for all of your help.
Before:
http://imgur.com/5ZrgvT7
https://imgur.com/oCGXwaf
After:
http://imgur.com/C7icxq6

X5 is back up and running. Wire is cool to touch. Battery is charging again.
Terminall was originally very corroded. When I attempted to clean the copper loop at end of wire, it disintegrated.

Sorry. I couldn't get images to load in the post.

X5M-ISH 06-02-2019 12:52 AM

Quote:

Originally Posted by sevet (Post 1162960)
X5 is back up and running.

Much better. That other cable was pretty bad. Oxidization is like a cancer and can spread. While your cable end and nut are copper, the post is still some blend of felsic metal. The potential for electrolysis and oxidizaton still exists. If you’re in an area where the DOT salts the roads or are living on the coast, consider using a dialectic grease on all your grounds, battery terminal and alternator. The grease is hydrophobic and keeps the connections from corroding. Just dab it on your finger and thumb and smear it around.


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